As a related device, there has been provided a lighting device that is configured to supply solid light sources with a pulsating voltage derived from an AC (alternating-current) voltage supplied from an AC power supply, thereby lighting the solid light sources (see, e.g., an LED driver circuit described in JP 2013-55168A (hereinafter referred to as “Document 1”)). The lighting device (LED driver circuit) described in Document 1 includes a full-wave rectifier circuit composed of diodes, a first bypass circuit, a first LED array, a second bypass circuit, a second LED array and a constant current circuit. Each of the first and second LED arrays is formed of a series circuit of LEDs.
Two input terminals of the first bypass circuit are electrically connected one-to-one with two pulsating output terminals of the full-wave rectifier circuit. A positive end (anode) of the first LED array is electrically connected to a high potential side output terminal of the first bypass circuit. A negative end (cathode) of the first LED array is electrically connected to a high potential side input terminal of the second bypass circuit. A low potential side output terminal of the first bypass circuit is electrically connected to a low potential side input terminal of the second bypass circuit. A positive end (anode) of the second LED array is electrically connected to a high potential side input terminal of the second bypass circuit. A negative end (cathode) of the second LED array is electrically connected to an input terminal of the constant current circuit. A low potential side output terminal of the second bypass circuit is electrically connected to an output terminal of the constant current circuit. Each of the first and second bypass circuits is composed of transistors, resistors and the like.
The lighting device described in Document 1 is configured so that the first bypass circuit allows a first bypass current to flow through during a period of time while no current flows through the first LED array, thereby reducing harmonic distortion of comparatively lower harmonics that may occur in an input current.
Incidentally, in the first bypass circuit in the related device described in Document 1, the two input terminals are electrically connected one-to-one with the two pulsating output terminals of the full-wave rectifier circuit. The first bypass circuit accordingly needs, as a component thereof, a transistor having a blocking voltage higher than a peak voltage of the pulsating voltage, which causes a rise in production cost.